1. Brief Description of the Invention
The present invention concerns compositions, and kits including same, suitable for use in priming a plastic surface for adhesion of a filler material to the plastic surface. More specifically, the compositions and kits of the invention include solvents which wet and penetrate but are not substantially retained by the plastic surface to allow a "featheredge" boundary between the filler and plastic.
2. Related Art
Recent advances in plastic injection molding technology has made it possible to form plastic auto body parts having high impact strength that are corrosion resistant. Two dominant forms of plastic materials used for bumper facie are reaction injection molded (RIM) urethane plastics and "thermoplastic polyolefins", more commonly referred to as "TPO". The use of such plastic auto body parts has resulted in an increasing demand for improved methods for repairing cracks, gouges, holes, and the like resulting from accidental damage. In order to produce an aesthetically pleasing repair, the boundary between the repaired region and the undamaged surface is preferably invisible when the auto body part is refinished, typically painted. Consequently, body fillers must adhere tenaciously to the plastic surface if the boundary is to be sanded perfectly smooth. At the sanded boundary region between filler and plastic, the filler material is extremely thin and tapered, producing what is commonly referred to as a "featheredge". The adhesion of the filler to the plastic substrate at this featheredge is critical in achieving an "invisible" repair acceptable to the customer.
Various types of primers have been developed which enhance featheredge adhesion between particular plastic and filler combinations, such as solvent-based solutions and water-based dispersions of chlorinated polyolefins which are effective in increasing the adhesion of epoxy fillers to TPO plastics, however chlorinated polyolefins are not known to be effective in increasing the adhesion of the epoxy fillers to other plastics. The inventor is not aware of a "universal" primer that effectively promotes adhesion between a wide range of plastic substrates and filler materials.
In a typical body shop, when a plastic auto body part is to be repaired, it must first be determined what the composition of the plastic body part is. This is because if the plastic autobody part is made of TPO, and if an epoxy body filler is to be used, the body part will typically require the use of a polyolefin adhesion promoter to achieve an effective repair. If the body part is RIM urethane, the epoxy filler material may be used without the adhesion promoter.
One typical test used to determine the composition of the plastic auto body part is to clean the area to be repaired with soap and water, followed by removal of any grease, wax and/or tar with a general purpose adhesive cleaner. The repair area is then typically ground with a high rpm sander, tapering into the damaged area. If the plastic body part grinds cleanly with no melted plastic next to the repair area, then the repair person knows that the automobile part is made of RIM urethane. If the grinding operation melted the plastic (i.e., there is actually melted plastic next to the area that was ground), the part requires the use of the polyolefin adhesion promoter, typically for both the repair material and any subsequent priming and/or painting operations. Therefore, it would be advantageous if a "universal" primer would be developed which would allow body fillers to be used with a variety of plastic automobile parts, including both RIM urethane and TPO, without having to first determine the composition of the plastic automobile part.